The year 2022 will go down in the books as a fantastic wasp year. Based on reports of wasp nests to pest controllers and wasp observations, we conclude that the previously announced expectation that we are heading for a wasp-rich summer is coming true. Various combatants report that it is a peak year. Some have not had such a good year in their nearly twenty years of operation. On the other hand, there are also opponents who state that it is busier than usual, but not extremely so. As always, the wasp population varies regionally.
Many wasps one year often lead to fewer wasps the next year
The number of wasps varies greatly from year to year. An analysis of 39 years of wasp trapping by the common wasp in Great Britain and 23 years of observations of wasp nest density per hectares in New Zealand shows that a good wasp year is often followed by a bad wasp year. And vice versa: a bad wasp year is followed by a good wasp year.
In the Netherlands we had a very bad year for wasps in 2021. So it was a good starting point for many wasps this year. One reason for this relationship is that with many wasps there is more competition for food between wasp colonies. As a result, newly formed queens have less energy to survive the winter and form a new nest in the new year. Another reason could be that the pressure of diseases and parasites is higher when there are many wasps, which means that fewer queens manage to survive the winter and/or start nesting. Based on the large numbers this year, we can therefore expect fewer wasps next year.
Warm winter and warm spring favorable
In addition to the number of wasps in the previous year, there are also other factors that determine whether there are many or few wasps. The weather is also an important factor. The English study mentioned above showed that the higher the temperature in winter and spring, the higher the number of common wasps will be that year. The last winter temperature of 5.7° Celsius is the sixth warmest on record since 1901. Spring came on the 17th with 10.2° Celsius.that Place. Both are therefore beneficial for wasps. In addition, it was also very dry in the spring, which was good for the queens, who are very vulnerable to bad weather in the first month after waking from hibernation.
Wasps attract other wasps
In the coming weeks, we will probably come across quite a few wasps. How to prevent wasp damage is therefore a frequently asked question. In a previous nature report, we already gave an overview of what wasps don’t like to smell. Smell is important for wasps when they need to find treats. However, their views also have a great influence. Experimental research shows that wasps fly faster towards objects if they see more wasps around such an object. Even fake wasps have the same effect. It is therefore advisable not to hang a wasp trap on or directly next to your terrace. The trap attracts wasps, and the presence of wasps around the trap attracts other wasps.
Dark moving objects more attractive
That wasps are very visually oriented is also evident from a German study that looked at how color and movement affected the extent to which wasps attacked. Moving black balls in front of a nest opening are much more likely to be flown in by wasps than white balls hanging still. So it is better not to wear clothes with black elements when sitting on the terrace. Fast movements also give wasps an extra strong alarm.
Scent of toxins alerts other wasps
The German study mentioned above also showed that the release of venom when stinging alerts other wasps. If venom from the sting of a dead wasp was applied to one of the two black spheres in front of a nest opening, the poisoned sphere was attacked much more often. The more venom released, the more wasps will attack. The more often an animal or person is stung, the more wasps will be attracted to it. The scent of the venom helps wasps locate the enemy. It is striking that the color is more decisive in the choice of which object to attack. A black ball without toxins was attacked much more often than a white ball with toxin applied.
When you kill a wasp, the stinger often comes out with some poison. To alert as few other wasps as possible, it is recommended to wipe the surface where the wasp was struck with soapy water.
From chewers, via rodents, hunters and water carriers to guards
Besides being a nuisance, wasps are also fascinating animals. For example, the way a wasp colony and the accompanying wasp nest develops is impressive. An important success factor is the division of labor between the workers. Workers perform various tasks throughout their lives. Once they have pupated, they stay in the nest for some time. They are then fed by older workers and they eat the nutritious saliva secreted by the larvae (see below for more information). Over time, they help chew (pre-chew) the meat that other workers have brought. Then they give it to the boy. After some time they fly out. During the first fifteen days, they mainly collect wood pulp with which the nest can be repaired and/or expanded. You see and hear them gnawing on wooden garden furniture, fences or tree bark. After day ten, they focus more on hunting insects and spiders. Around day twenty, they spend a quarter of their flight hunting. As they get older, they become more and more engaged in collecting moisture. One-month-old workers almost never leave the nest and stay at the entrance to guard the nest.
Larval saliva even more nutritious than nectar
When the larvae get food from a worker bee, they give a drop of saliva to the worker bee as a kind of reward. Chemical analyzes of this saliva show that it is very nutritious and full of sugars and all kinds of amino acids. Amino acids are the building blocks of proteins. The concentration and number of amino acids in larval saliva is usually (much) higher than what is found in nectar. Wasps also visit flower species that produce nectar with a higher amino acid concentration than butterflies, flies and bees. In addition to the workers, the queen is also dependent on the saliva produced by the larvae.
Lays 300 eggs a day
The amino acids appear to be an important source for the queen’s continuous production of new eggs. A wasp queen is capable of laying around 300 eggs per day when the nest is fully developed. An egg hatches after about five days. The number of queens raised by a nest varies from 750 in a small one to as many as 2000 in a large wasp nest.
More wasp genes due to lack of nutrient-rich larval saliva
When the nest is fully grown and the number of larvae decreases, there is also less saliva available for the workers. To compensate for this, they look for other sources. When the weather is nice and we spend a lot of time outside, our food and drinks are a welcome and convenient source. This is when the wasp sting occurs.
Several hundred meters
The workers collect food within a few hundred meters of the nest. Sometimes they go further than a kilometer. Wasps follow each other to find food sources. They cannot, as bees do, tell each other where to find food in any other way.
Workers can live more than a month
The more flights a worker bee makes, the shorter she lives. During the rapid nest expansion in July and early August, many flights are performed and a worker bee lives an average of 14 days. In August, the average age rises to 22 days. In the breeding phase of the new queens, from the end of August and in September, the average age drops back to 17 days.
Light enough to fly
Wasps orient themselves when they fly on objects. If it is too dark, they can no longer find their way. The light intensity at which wasps decide to fly in the morning is lower than when they decide not to leave the nest in the evening. The wasps probably don’t want to run the risk of not being able to find their way back in the evening. The wasps that return to the edge also regularly fly into small objects and other wasps as they seek the entrance to the nest. During a foggy morning, the wasps only start flying when the light intensity is sufficient. But as long as important landmarks are not (well) visible, they stay close to the nest.
Early in the morning the number of arrivals peaks
Wasps that fly back too late spend the night outside. It is these wasps that cause a peak in the number of wasps entering the nest in the early hours of the morning.
Use of wasps
A Dutch study from the 1960s showed that the common wasp brought a huge diversity of insect and spider species to the nest. It turned out to be more than thirty species of insects and eight species of spiders. These included earwigs, grasshoppers, dragonflies, true insects, beetles, hymenoptera and flies. Flies seem to be the most preferred prey. Mosquitoes are also part of this. In some colonies more than 80 percent of the prey consisted of flies. In some colonies, more than 40 percent of the prey was found to consist of spiders. In other colonies, more than 40 percent of the prey consisted of larvae such as caterpillars and maggots. Another German study from the 1960s found that 63 percent of the prey from a colony of German wasps was flies. It was primarily about the day fly. Butterflies made up 14 percent, bees 4 percent and spiders only 2 percent. Wasps are also sometimes used as natural predators because they hunt, for example, houseflies, small houseflies, blood-drinking houseflies and horseflies and whiteflies. Having many wasps in the area can greatly reduce the nuisance caused by these other insects. So when you come across a wasp nest, consider whether it is really necessary to have the nest removed.
Text: Arnold van Vliet, Wageningen University
Photos: Gerbert Kets, Arnold van Vliet